Mechanisms of Viral Resistance Mediated by MAP3K7 and CHD1 in Prostate Cancer A virus must evade or inhibit the defenses deployed by the host cell in order to replicate. This struggle between host and pathogen is a determinant of viral tissue tropism and pathogenicity. Vesicular stomatitis virus (VSV), the prototype rhabdovirus, is a virus whose tissue tropism is dictated by the host anti-viral response, and VSV's success or failure in suppressing that response. For example, VSV selectively infects the immune-impaired cells of cancer tissue. This is the basis for the use of VSV and other viruses as potential oncolytic virus therapies. VSV is able to infect most cancers, however some cancers maintain resistance to VSV infection by constitutively expressing anti-viral genes. Prostate cancers (PCa) display variable levels of resistance to viral infection. Our laboratory has shown that PC-3 cells constitutively express anti-viral gene products. Our data indicate that this is the result of a novel anti-viral signaling mechanism that is mediated by the gene products of MAP3K7 and CHD1. When these genes are silenced, PC-3 cells become more susceptible to viral infection. RNA-Seq analysis shows that silencing CHD1 or both MAP3K7 and CHD1 decreases anti-viral gene mRNA expression, but silencing MAP3K7 alone increases it. Silencing MAP3K7 decreases phosphorylation of STAT1. This suggests that MAP3K7 regulates anti-viral gene expression in a post-transcriptional manner. Viral susceptibility and anti-viral gene expression will be measured in PC-3 cells in which MAP3K7 and/or CHD1 have been knocked out with the CRISPR/Cas9 system. The mechanism of post-transcriptional regulation of anti-viral genes by MAP3K7 will be determined through Polysome-Seq and proteasome inhibition. Downstream mediators of the anti-viral effect of MAP3K7 and CHD1 will be identified with ChIP-Seq. Finally, xenografts of PC-3 tumors with MAP3K7, CHD1, or both knocked out will be established in mice. The mice will be treated with intravenous VSV, and any effect of MAP3K7 or CHD1 on the tumors' response will be determined.